1. Field of the Invention
The present invention relates to apparatus and methods for evolving a 5 volt signaling environment to a 3.3 volt signaling environment. More particularly, the present invention relates to the evolution of a bus system with connectors having circuits configured for 5 volts to a bus system which is capable of supporting both 5 volt as well as 3.3 volt circuit devices.
2. Art Background
Over the past two decades, semiconductor devices, and bus systems to which these devices are coupled, have been developed based on 5 volt (V.sub.cc) specification and signaling technology. Most microprocessors, memories and other digital electronic components operate using a 5 volt V.sub.cc which has become a standard throughout the world. Personal computers, workstations and many other electronic systems utilize 5 volt V.sub.cc signaling and switching environments.
The development and implementation of process technology based on a V.sub.cc of 3.3 volts promises significant power savings in future systems. As a result of the advantages of 3.3 volt process technology and signaling environments, manufacturers are now producing semiconductor components such as central processing units (CPUs) and memory devices based on this new 3.3 volt V.sub.cc standard. However, the use of 3.3 volt technology presents compatibility problems for existing 5 volt V.sub.cc systems. Although it is likely that 5 volt systems will be phased out in the future in favor of the 3.3 volt signaling standard, it is not cost effective to immediately phase out 5 volt systems since there is a significant base of existing technology currently in use throughout the world.
As will be described, the present invention provides a method and apparatus for transition from a 5 volt to a 3.3 volt signaling environment in a bus system with connectors by allowing a connector with a key to accept an add-in board with a mating key and by providing predetermined I/O power pins in the connector so that the voltage signaling environment of the add-in board can be adapted to the voltage signaling environment of the connector.